Change Audio Speed Online
Speed up or slow down any audio file from 0.25x to 4x. Preview the new duration, adjust the speed, and download. Free, private, and entirely browser-based. Your files never leave your device.
Drop files here or browse
Supports MP3, WAV, OGG, AAC, M4A, FLAC - up to 500 MB
Tips for changing audio speed
0.25x to 4.0x speed range
Slow down to 0.25x for dramatic effect or speed up to 4x for time-lapse audio. Multiple atempo filters chain automatically for extreme speeds.
Natural-sounding audio
FFmpeg's atempo filter adjusts both speed and pitch for natural-sounding results. No chipmunk voices or deep rumbles.
Preserves original format
Output keeps the same format (MP3, WAV, OGG, AAC, FLAC) as the input.
Preview before processing
Listen to the original audio before changing speed. See the new duration calculated instantly.
Privacy first
All speed changes happen in your browser using WebAssembly. Your audio files are never uploaded anywhere.
How to change audio speed online
Whether you need to slow down a podcast for transcription, speed up a voice recording for a time-lapse, or adjust the tempo of a music track to fit a project, this free audio speed changer handles it all directly in your browser.
The tool uses FFmpeg WebAssembly with the atempo filter to adjust playback speed. The atempo filter maintains natural-sounding pitch throughout the speed adjustment range. For speeds outside the reliable 0.5-2.0x range (where atempo works best alone), multiple filters are chained automatically to produce consistent, natural results from 0.25x to 4.0x.
The first use requires a one-time download of the audio engine (~30 MB), after which subsequent speed changes start immediately. All processing happens locally in your browser — your audio files are never uploaded to any server.
Frequently asked questions
How do I change audio speed?
Upload your audio file, choose a speed preset (0.5x to 2.0x) or enter a custom speed (0.25x to 4.0x), and click Change Speed. Preview the original and see the new duration before processing.
Is my audio uploaded to a server?
No. All speed changes happen locally in your browser using WebAssembly (FFmpeg.wasm). Your files never leave your device.
What audio formats are supported?
The tool supports MP3, WAV, OGG, AAC, and FLAC input and output formats. The output is saved in the same format as the original.
Will changing speed affect audio quality?
The atempo filter maintains natural pitch while adjusting speed. Some minimal quality difference may occur from the processing, but it should be imperceptible for most use cases.
What's the speed range?
You can slow down to 0.25x or speed up to 4.0x. For speeds outside the reliable 0.5-2.0x range, multiple atempo filters are chained automatically for natural-sounding results.